Uranium-232 has a half-life of 68.9 years. A sample from 206.7 years ago contains 1.40 g of uranium-232. How much uranium was originally present?

How do catalysts increase the rate of a chemical reaction? A] They lower the activation energy. B] They lower the collision energy. C] They increase the collision energy. D] They increase the temperature.

How to balance equations

How many moles are in 25g of HF

What is a group in the periodic table of elements? Question 4 options: the elements that have the same atomic number the elements that have similar densities and atomic sizes the elements that are in the same column of the periodic table of elements

which of these is an example of a chemical change A breaking glass B mealting ice on a windshield C burning gasoline D denting a bumper

What element has 8 valence electrons

Which of the following best describes a metal? Brittle, shiny, and solid Brittle, dull, and low density Malleable, shiny, and able to conduct heat or electricity Malleable, dull, and solid, liquid, or gas at room temperature?

Which of the following errors could cause your percent yield to be falsely high, or even over 100%? Select ALL that apply. A.) Heating the sample too vigorously. B.) Handling the crucible directly with your hands. C.

If 56.8 ml of bacl2 solution is needed to precipitate all the sulfate ion in a 554 mg sample of na2so4 (forming baso4), what is the molarity of the solution?

is the number of total atoms on the left side of a balanced equation always equal to the number of total atoms on the right side of the equation?